Manufacturing method for molded products

Abstract

To realize a manufacturing method for molded products with excellent release properties. [Solution] The molding surfaces (31A, 32A) of the mold (30) used in the method for manufacturing a molded body have an average length RSm in the range of 100 μm to 400 μm.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a molded body.

Background Art

[0002] Many molding techniques are known in which a resin composition containing a thermoplastic resin is molded using a mold. For example, in Patent Document 1, a poly(3-hydroxyalkanoate)-based resin, which is a biodegradable thermoplastic resin, is heated to form a molten resin, and the molten resin is quantitatively discharged into a pair of molds, and the pair of molds is closed and press-molded to obtain a molded body. A press molding technique is known. Further, Patent Document 2 discloses a molding technique for manufacturing a light reflection molded body by thermally molding a light reflection plate formed from a thermoplastic resin sheet using a mold.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, among the conventional techniques as described above, especially the technique of Patent Document 1 is an excellent technique. However, as a result of the inventors' own studies, it has been found that the technique of Patent Document 1 may have a problem that the molded body is difficult to be removed from the mold (poor mold release property), and there is room for improvement.

[0005] One aspect of the present invention aims to realize a method for manufacturing a molded body having excellent mold release property.

Means for Solving the Problems

[0006] To solve the aforementioned problems, a method for manufacturing a molded article according to one aspect of the present invention includes a molding step of molding a resin composition containing a thermoplastic resin using a mold, wherein the molding surface of the mold has an average length RSm in the range of 100 μm to 400 μm.

[0007] To solve the aforementioned problems, a manufacturing apparatus for a molded article according to one aspect of the present invention is a manufacturing apparatus comprising a mold for molding a resin composition containing a thermoplastic resin, wherein the molding surface of the mold has an average length RSm in the range of 100 μm to 400 μm. [Effects of the Invention]

[0008] According to one aspect of the present invention, a method for manufacturing a molded article with excellent release properties can be realized. [Brief explanation of the drawing]

[0009] [Figure 1] 101 is a cross-sectional view showing the schematic configuration of an example of a pair of molds used in a method for manufacturing a molded article according to one embodiment of the present invention, and 102 is a cross-sectional view showing the schematic configuration of a press-formed article press-formed by the pair of molds shown in 101. [Figure 2] This figure schematically shows the general configuration of a manufacturing apparatus according to one embodiment of the present invention. [Modes for carrying out the invention]

[0010] One embodiment of the present invention will be described in detail below. Unless otherwise specified in this specification, "A to B" representing a numerical range means "greater than or equal to A and less than or equal to B". Furthermore, all references cited in this specification are incorporated herein by reference.

[0011] [Technical philosophy] The inventors have been diligently studying a method for manufacturing molded articles in which a molten resin obtained by heating a thermoplastic resin is press-molded while remaining in a molten state that can flow within the mold. For example, in the technology described in Patent Document 1, when manufacturing a molded article with a shallow bottom structure such as a lid, the release properties are improved by setting the arithmetic mean roughness Ra and maximum height Rz of the molded surface (the surface in contact with the molten resin) to a predetermined range.

[0012] The inventors further researched the optimal mold surface for releasing deep-bottomed molded bodies, such as cups, in the aforementioned press molding method. In the course of this research, the inventors discovered a new problem: even when applying the technology of Patent Document 1 to the manufacture of deep-bottomed molded bodies, a vacuum is created between the molded body and the mold surface, resulting in strong adhesion and making it difficult to release the molded body from the mold. Therefore, the inventors investigated the specification of surface roughness that can break the vacuum between the bottom-structured molded body and the mold surface, and focused on the "average length RSm of roughness curve elements" (hereinafter simply referred to as average length RSm), which defines the pitch between the peaks and valleys in the uneven shape of the molded surface. They then found that by surface treating the mold surface and setting the average length RSm of the roughness curve elements of the molded surface within a certain range, excellent release properties (mold release properties) can be achieved when manufacturing deep-bottomed molded bodies.

[0013] In other words, a method for manufacturing a molded article according to one embodiment of the present invention (hereinafter referred to as the "production method") was obtained based on the above findings, and includes a molding step of molding a resin composition containing a thermoplastic resin using a mold, wherein the molding surface of the mold has an average length RSm in the range of 100 μm to 400 μm.

[0014] Furthermore, the manufacturing apparatus for a molded article according to one embodiment of the present invention (hereinafter referred to as "the manufacturing apparatus") is equipped with a mold for molding a resin composition containing a thermoplastic resin, and the molding surface of the mold has an average length RSm in the range of 100 μm to 400 μm.

[0015] According to this manufacturing method and apparatus, the molding surface of the mold has an average length RSm within the range of 100 μm to 400 μm, resulting in excellent mold release properties when manufacturing deep-bottom molded bodies. Furthermore, this manufacturing method and apparatus are applicable not only to the manufacture of deep-bottom molded bodies but also to molded bodies of any structure. This manufacturing method and apparatus are also applicable to the manufacture of shallow-bottom molded bodies.

[0016] Furthermore, this manufacturing method and apparatus are applicable to known molding techniques as long as a resin composition containing a thermoplastic resin is molded using a mold. Molding techniques to which this manufacturing method and apparatus are applicable include, in addition to the press molding using molten resin described above, injection molding, vacuum molding, blow molding, and the like. Moreover, when molding using a mold in this manufacturing method and apparatus, the resin composition may be introduced into the mold in any state; it may be introduced into the mold in a fluid molten state as described above, or it may be introduced into the mold in the form of a sheet. This manufacturing method and apparatus are also applicable to vacuum molding using a resin sheet containing a resin composition.

[0017] Furthermore, the resin composition used in this manufacturing method and apparatus includes a thermoplastic resin. The thermoplastic resin is not particularly limited. Preferred thermoplastic resins include general-purpose resins such as polypropylene, polyethylene, polyvinyl chloride, polyvinyl acetate, polyacetal, polycarbonate, polyamide, acrylonitrile, butadiene, polystyrene, and acrylic polymers, as well as biodegradable resins such as poly(3-hydroxyalkanoate) resins, polylactic acid, polyglycolic acid, polybutylene succinate, polybutylene succinate adipate, polybutylene adipate terephthalate, polybutylene succinate terephthalate, and polycaprolactone.

[0018] The thermoplastic resin is more preferably a poly(3-hydroxyalkanoate) resin (hereinafter referred to as a P3HA-based resin). Thereby, marine pollution due to waste can be suppressed, and for example, it can contribute to the achievement of sustainable development goals (SDGs) such as Goal 12 "Ensure sustainable consumption and production patterns" and Goal 14 "Conserve and use the oceans and marine resources for sustainable development in a sustainable manner".

[0019] Hereinafter, the case where the manufacturing method and the manufacturing apparatus are applied to press molding using a resin composition containing a P3HA-based resin as the resin composition and using the above-mentioned molten resin will be described. In this case, this manufacturing method includes a heating step of heating a resin composition containing a P3HA-based resin to obtain a molten resin composition, a resin supply step of supplying the molten resin composition between a pair of molds by discharging the molten resin composition from a discharge portion, and a press molding step of closing the pair of molds to press-mold and cool the flowable molten resin composition. It can be said that it is a method in which the molding surfaces of the pair of molds have an average length RSm within the range of 100 μm to 400 μm. Further, this manufacturing apparatus is a manufacturing apparatus for a press-molded body provided with a pair of molds filled with a molten resin composition containing a P3HA-based resin, and includes a molten resin generation portion that heats the P3HA-based resin composition to generate a molten resin composition, a discharge portion that discharges the molten resin composition, and a supply portion that supplies the molten resin composition between the pair of molds by the discharge portion, and a molding portion that closes the pair of molds to press-mold and cool the flowable molten resin composition. It can be said that it is an apparatus in which the molding surfaces of the pair of molds have an average length RSm within the range of 100 μm to 400 μm.

[0020] 〔Manufacturing method of (press) molded body〕 This manufacturing method has, as described above, a heating step, a resin supply step, and a press molding step. In this manufacturing method, a press-molded body of a P3HA-based resin is manufactured through the heating step, the resin supply step, and the press molding step.

[0021] In the heating step, a resin composition containing a P3HA-based resin is heated to obtain a molten resin composition. As the heating method of the resin composition, a conventionally known method can be adopted as long as it can form a molten resin composition containing a P3HA-based resin. Preferably, the heating step includes a melt-kneading step of melt-kneading a resin composition containing a P3HA-based resin.

[0022] The mode of the melt-kneading step is not particularly limited as long as a melt-kneaded resin composition can be obtained. Specific examples of the melt-kneading step include, for example, the methods of (a1) and (a2) below: (a1) A resin composition containing a P3HA-based resin is prepared by mixing or blending with a mixing device or the like. Then, the resin composition is supplied to a melt-kneading device and melt-kneaded; (a2) Raw materials of a resin composition containing a P3HA-based resin are supplied to a melt-kneading device, and the resin composition is prepared (completed) in the melt-kneading device and at the same time, the resin composition is melt-kneaded.

[0023] In the method of (a1), the order of mixing or blending (dry blending) the raw materials of the resin composition containing a P3HA-based resin is not particularly limited. In the method of (a2), the order of supplying the raw materials of the resin composition containing a P3HA-based resin to the melt-kneading device is not particularly limited.

[0024] In the method of (a1), the mixing device is not particularly limited, and examples include a ribbon blender, a flash blender, a tumbler mixer, a super mixer, and the like.

[0025] In the methods of (a1) and (a2), the melt-kneading device is not particularly limited, and examples include an extruder, a kneader, a Banbury mixer, and rolls. From the viewpoint of excellent productivity and convenience, an extruder is preferably used as the melt-kneading device, and a twin-screw extruder is more preferably used.

[0026] In the melt-mixing process, the temperature at which the resin composition is melt-mixed cannot be specified in general terms, as it depends on the physical properties of P3HA (melting point, weight-average molecular weight, etc.) and the type of additives used. Regarding the temperature at which the resin composition is melt-mixed, for example, it is preferable that the temperature of the melt-mixed resin composition discharged from the discharge unit (hereinafter sometimes referred to as the composition temperature) be 140°C to 190°C, more preferably 150°C to 180°C, and even more preferably 160°C to 170°C. If the composition temperature is 150°C or lower, unmelted P3HA resin may be generated. On the other hand, if the composition temperature is 180°C or higher, the P3HA resin may undergo thermal decomposition.

[0027] Furthermore, in the resin supply process, the molten resin composition is supplied between the pair of molds by being discharged from the discharge unit. In the resin supply process, the molten resin composition is discharged from the discharge unit to the pair of molds while still in a molten state. This supplies the molten resin composition between the pair of molds.

[0028] The method for supplying the molten resin composition between the molds is not particularly limited, as long as the molten resin composition discharged from the discharge unit can be supplied between the pair of molds. From the viewpoint of reliably supplying the molten resin composition between the pair of molds, it is preferable to first discharge the molten resin composition from the discharge unit to the lower mold, supply a predetermined amount of the molten resin composition to the lower mold, and then place the upper mold on the lower mold to supply the molten resin composition between the pair of molds.

[0029] Furthermore, in the resin supply process, the configuration of the discharge unit is not particularly limited as long as it is capable of discharging the molten resin composition, and conventionally known configurations can be adopted. From the viewpoint of improving the productivity of press-molded products, it is preferable that the discharge unit is configured to be capable of quantitatively discharging the molten resin composition. Examples of such discharge unit configurations include configurations equipped with a gear pump and configurations equipped with an automatic opening and closing nozzle. Specific examples of discharge units include plunger-type dischargers, pre-plunger-type dischargers, and screw-type dischargers.

[0030] Furthermore, in the press molding process, the pair of molds are closed and the flowable molten resin composition is press-molded and cooled. In the resin supply process, the molten resin composition is supplied between the pair of molds while still in a molten state, so even when the pair of molds is closed in the press molding process, the molten resin composition can flow through the space between the pair of molds.

[0031] In the resin supply step, the molten resin composition is supplied between the pair of molds. In the press molding step, a hot press is performed on the pair of molds using a hot press molding machine. Press molding is then carried out by cooling the pair of molds after the hot press is completed. After press molding, the pair of molds are opened to obtain a press-molded body.

[0032] The hot press molding machine used in the resin supply process is not particularly limited, as long as it is configured to hot press the pair of molds to which the molten resin composition is supplied. Conventional known devices can be used as the hot press molding machine.

[0033] The method for cooling a pair of molds after hot pressing is not particularly limited. For example, one method involves clamping the pair of molds after hot pressing with a pair of cooling plates and then performing a cooling press.

[0034] In this method, the press pressure during cooling press is not particularly limited, but is preferably 10KN to 300KN, and more preferably 40KN to 200KN. Setting the press pressure within the above numerical range has the advantage of obtaining a press-formed body with uniform thickness.

[0035] Furthermore, while the pressing time during cooling press is not particularly limited, it is preferably 30 to 600 seconds, and more preferably 60 to 300 seconds. Setting the pressing time within the above numerical range has the advantage that the P3HA resin solidifies sufficiently, making it easier to remove the press-molded product.

[0036] Furthermore, while the temperature of the cooling plate used in the cooling press is not particularly limited, it is preferably 10°C to 60°C, and more preferably 20°C to 50°C. Setting the temperature of the cooling plate within the above numerical range has the advantage that the solidification of the P3HA resin proceeds sufficiently, making it easier to remove the press-molded product.

[0037] Herein, as described above, this manufacturing method offers the advantage of excellent mold release properties when molding a deep-bottomed molded body. Therefore, it is preferable that the molded body produced by this manufacturing method has a deep-bottomed structure.

[0038] Figure 101 is a cross-sectional view showing a schematic configuration of an example of a pair of molds 30 used in this manufacturing method. Figure 102 is a cross-sectional view showing a schematic configuration of a press-formed body A that has been press-formed by the pair of molds 30.

[0039] As shown in Figure 1, 102, the press-molded body A produced by this manufacturing method is, for example, a rotationally symmetric, deep-bottomed cylindrical cup shape. The press-molded body A is cylindrical with side walls A2, with a bottom A1 formed at one end and an opening at the other end. A recess is formed in the central part of the bottom A1. The press-molded body A is not particularly limited as long as it is a rotationally symmetric, deep-bottomed cylindrical article, for example, a beverage cup.

[0040] Furthermore, this manufacturing method can be applied to the production of a thin, deep-bottomed, bottomed cylindrical press-molded body A with a small wall thickness. The wall thickness of the press-molded body A is preferably 0.1 mm to 0.6 mm, and more preferably 0.2 mm to 0.4 mm.

[0041] Furthermore, the press-formed body A to which this manufacturing method can be applied is not particularly limited, as long as it is a rotationally symmetric, deep-bottomed cylindrical shape. Examples of the shape of the press-formed body A include a cylindrical shape of a regular polygonal prism with a bottom, a cylindrical shape of a star-shaped polygonal prism with a bottom, and a cylindrical shape of a bottom. Examples of cylindrical shapes of regular polygonal prisms with a bottom include a cylindrical shape of a regular triangular prism with a bottom, a cylindrical shape of a regular hexagonal prism with a bottom, and examples of cylindrical shapes of star-shaped polygonal prisms with a bottom include a cylindrical shape of a star-shaped pentagonal prism with a bottom, a cylindrical shape of a star-shaped octagonal prism with a bottom.

[0042] Furthermore, the direction in which the side wall portion A2 of the press-formed body A to which this manufacturing method can be applied is not particularly limited. The side wall portion A2 may extend parallel to the axis of symmetry X of the press-formed body A, or it may extend in a tapered shape such that the spacing increases towards the opening, or it may extend in a tapered shape such that the spacing decreases towards the opening. In addition, a stepped portion may be provided in the side wall portion A2. By providing a stepped portion in the side wall portion A2, an improvement in the strength of the side wall portion A2 can be expected.

[0043] A deep-bottom structure refers to a cylindrical structure with a bottom, composed of an inner surface and an outer surface in the height direction, and having a height of 20 mm to 300 mm. In a deep-bottom structure, it is preferable that at least one of the inner surface and the outer surface is a single surface. For example, in the press-molded body A shown in 102 of Figure 1, the deep-bottom structure refers to a structure in which the ratio C / B of the diameter B of the bottom A1 to the dimension (height) C in the HD direction is 0.4 to 5.0. The ratio C / B is preferably 0.8 to 3.2, and more preferably 1.6 to 2.8. In addition, the dimension C in the HD direction is preferably 40 mm to 200 mm, and more preferably 80 mm to 160 mm.

[0044] The mold 30 has a molding space for forming a press-formed body A. This molding space is formed rotationally symmetric with respect to the axis of symmetry X. In the drawings of this application (Figures 1 and 2), the extension direction of the axis of symmetry X is defined as the HD direction (height direction), and the direction perpendicular to the HD direction is defined as the WD direction (width direction). The rotational direction around the axis of symmetry X is defined as the RD direction. The WD direction can be said to be the radial direction of the rotationally symmetrical shape of the press-formed body A. The RD direction can be said to be the outer circumference direction of the press-formed body A. Furthermore, one side (upper side) in the HD direction is defined as the HDa side, and the other side (lower side) is defined as the HDb side.

[0045] As shown in Figure 1, 101, the mold 30 consists of a cavity mold 31 and a core mold 32. The molding space is formed by the cavity mold 31 and the core mold 32. The molding space is formed by the molding surface 31A of the cavity mold 31 and the molding surface 32A of the core mold 32. The molding surface 31A has molding surfaces 31b and 31c that form the outer surface (outer side surface) of the side wall portion A2. The molding surface 32A has molding surfaces 32b and 32c that form the inner surface (inner side surface) of the side wall portion A2. Here, "molding surface" refers to the surface in a pair of molds that comes into contact with the molten resin composition, and can also be described as the opposing surfaces of the cavity mold 31 and the core mold 32 that face each other.

[0046] In the demolding process for releasing the press-formed body A from the mold 30 shown in Figure 1, first, a separation process is performed to separate the cavity mold 31 and the core mold 32. This separation process causes the press-formed body A to adhere to either the cavity mold 31 or the core mold 32. If the press-formed body A is adhered to the core mold 32, following the separation process, a moving process is performed to move the press-formed body A toward the HDa side and release the press-formed body A from the core mold 32.

[0047] The side wall portion A2 of the press-formed body A has no steps, and the outer and inner surfaces of the side wall portion A2 are composed of a single surface. Furthermore, compared to the press-formed body with a shallow bottom structure, the press-formed body A with a deep bottom structure has a longer contact area with the core mold 32 in the HD direction. Note that the side wall portion A2 of the press-formed body A is not limited to the structure shown at 102 in Figure 1, and may have steps.

[0048] Therefore, even if the surface friction force of the molding surface 32A of the core mold 32 is reduced to optimize the release properties of the press-molded body with a shallow bottom structure, the release properties of the press-molded body A deteriorate during the movement process because there is no starting point for release from the press-molded body A on the core mold 32. Here, the inventors discovered that when the surface friction force of the molding surface 32A is reduced, the press-molded body A can rotate in the RD direction relative to the core mold 32, but it is difficult to move in the HD direction. From this phenomenon, the inventors considered that the cause of the deterioration in the release properties of the press-molded body A as described above lies in the vacuum state between the molding surface 32A and the press-molded body A. That is, even if the surface friction force of the molding surface 32A is reduced, the press-molded body A can only rotate in the RD direction relative to the molding surface 32A, and even if the press-molded body A is moved towards the HDa side, it is difficult for air to enter between the molding surface 32A and the press-molded body A, and the vacuum state cannot be broken, so the release properties of the press-molded body A deteriorate during the movement process. Furthermore, this deterioration in the release properties of the press-molded body A can also occur when the press-molded body A is attached to the cavity mold 31 and is released from the cavity mold 31 during the transfer process.

[0049] Therefore, in this manufacturing method, the molding surface 31A and / or 32A (at least one of the molding surfaces 31A and 32A) of the mold 30 has an average length RSm in the range of 100 μm to 400 μm. Having the average length RSm within this range allows air to easily enter between the molding surface 31A and / or 32A and the press-molded body A during the transfer process, resulting in excellent release properties for the press-molded body A. The average length RSm is preferably 120 μm to 360 μm, and more preferably 140 μm to 240 μm. The average length RSm can be measured according to conventionally known methods, such as JIS B 0601-2001.

[0050] Furthermore, in this manufacturing method, the molding surface exhibiting the average length RSm within the range may be any molding surface among molding surfaces 31A and 32A to which the press-molded body A adheres after the separation step, preferably both molding surfaces 31A and 32A. Also, in molding surfaces 31A and / or 32A, the region exhibiting the average length RSm within the range may include at least the molding surfaces 31b·31c and / or 32b·32c that form the side wall portion A2, and more preferably the entire area of ​​molding surfaces 31A and / or 32A.

[0051] Furthermore, the press-molded body A suitable for this manufacturing method is not particularly limited, but is a molded body in which the thickness of the side wall portion A2 is 0.1 mm to 0.6 mm, preferably 0.2 mm to 0.4 mm.

[0052] Furthermore, in this manufacturing method, the arithmetic mean roughness Ra of the molded surface 31A and / or 32A may be any value, provided that the average length RSm is set to fall within the aforementioned numerical range. Preferably, the molded surface 31A and / or 32A has an arithmetic mean roughness Ra in the range of 0.1 μm to 3.0 μm and a maximum height Rz in the range of 0.5 μm to 20.0 μm. The arithmetic mean roughness Ra and maximum height Rz can be measured according to conventionally known methods, for example, JIS B 0601-2001.

[0053] By having the arithmetic mean roughness Ra and maximum height Rz of the molded surfaces 31A and / or 32A within the aforementioned numerical range, the molded surfaces 31A and / or 32A exhibit excellent release properties. When manufacturing a press-molded body with a shallow bottom structure, as in the technology described in Patent Document 1, even if the arithmetic mean roughness Ra of the molded surfaces 31A and / or 32A is made relatively small and the average length RSm is made relatively small, excellent release properties can be obtained. However, if such settings for arithmetic mean roughness Ra and average length RSm are applied to the manufacture of a press-molded body with a deep bottom structure, the release properties deteriorate (see Comparative Examples 1 to 4 described later). This is thought to be because a gap is less likely to form between the molded surfaces 31A and / or 32A and the press-molded body A, and the vacuum state cannot be broken.

[0054] On the other hand, in this manufacturing method, the average length RSm is set to be relatively large, and the arithmetic mean roughness Ra is also set to be relatively large, so a gap is easily created between the molded surface 31A and / or 32A and the press-molded body A, creating an air passage and improving release properties.

[0055] The arithmetic mean roughness Ra of the molded surface 31A and / or 32A is more preferably greater than 1.0 μm and 2.6 μm or less, and particularly preferably between 1.2 μm and 2.4 μm. The maximum height Rz of the molded surface 31A and / or 32A is more preferably between 2.0 μm and 16.0 μm, and particularly preferably between 4.0 μm and 14.0 μm.

[0056] Furthermore, it is preferable that the surface free energy of the molded surface 31A and / or 32A is 26.0 mN / m or less. More preferably, the surface free energy of the molded surface 31A and / or 32A is 22 mN / m or less, and even more preferably 18 mN / m or less. Furthermore, there is no particular lower limit to the surface free energy of the molded surface 31A and / or 32A, but it is preferable that it is 10 mN / m or more, and more preferably 12 mN / m or more.

[0057] Because the surface free energy is within the specified numerical range, when manufacturing press-molded articles of P3HA resin, excellent release properties are achieved, and the press molding temperature or press molding pressure can be reduced. Furthermore, even when the press molding pressure is low or the mold temperature during press molding is low, the mold 30 closes during press molding in a short hot pressing time, and the film thickness of the press-molded article A can be made to the designed film thickness. Therefore, the molding time can be shortened.

[0058] The surface free energy can be calculated as follows: First, using a contact angle meter, pure water and diiodomethane (CH2I2) are dropped onto the molded surface, and the contact angle θ between each droplet and the mold surface is measured. From the measured contact angle θ, the surface free energy of the molded surface is calculated using the Owens-Wendt method.

[0059] The heating temperature of the mold 30 during press molding (press molding temperature) should be any temperature that can maintain the composition temperature of the molten resin composition, preferably below the composition temperature of the molten resin composition, and more preferably between the composition temperature of the molten resin composition - 100°C and the composition temperature of the molten resin composition. According to this manufacturing method, the molding time can be shortened even at a relatively low press molding temperature within the above range.

[0060] Furthermore, the press molding pressure of the mold 30 by the hot press molding machine is not particularly limited, but is preferably 10KN to 300KN, and more preferably 40KN to 200KN. Even with a relatively low press molding pressure within the above numerical range, the molding time can be shortened.

[0061] Furthermore, the hot pressing time of the mold 30 by the hot press molding machine is not particularly limited, but is preferably 1 to 60 seconds, and more preferably 3 to 20 seconds. Even if the hot pressing time is set to a relatively short range as described above, the molding time can be shortened.

[0062] Furthermore, the molded surfaces 31A and / or 32A (hereinafter simply referred to as the molded surfaces) may be subjected to any surface treatment, provided that the average length RSm is within the aforementioned numerical range.

[0063] Furthermore, the molded surface may be roughened in order to form a molded surface exhibiting an average length RSm within the aforementioned numerical range. This roughening treatment can be carried out using conventionally known methods, but preferably it is at least one surface treatment selected from shot peening and blasting.

[0064] Shot peening is a surface treatment that creates irregularities on the mold molding surface by projecting spherical particles onto the surface using air pressure and causing them to collide. This shot peening process evens out the surface roughness of the mold molding surface and imparts compressive residual stress. In the shot peening process, various conditions such as the material and diameter of the spherical particles, the projection angle and speed (i.e., air pressure), and the processing time are not particularly limited and can be appropriately set according to the set values ​​of the average length RSm, arithmetic mean roughness Ra, and maximum height Rz.

[0065] Blasting is a surface treatment that forms irregularities on the mold surface by projecting, for example, polygonal particles onto the mold surface using air pressure and causing them to collide. In this manufacturing method, blasting is similar to shot peening in that it forms irregularities on the mold surface, but differs from shot peening in that it does not impart compressive residual stress to the mold surface. In blasting, various conditions such as the material and diameter of the polygonal particles, the projection angle and speed (i.e., air pressure) of the spherical particles, and the processing time are not particularly limited and can be appropriately set according to the set values ​​of the average length RSm, arithmetic mean roughness Ra, and maximum height Rz.

[0066] Furthermore, in this manufacturing method, it is preferable that the mold surface is treated with a silicon-based coating. This silicon-based coating improves the slipperiness of the molten resin composition against the mold surface. Therefore, even if the press molding temperature or press molding pressure is reduced, the fluidity of the molten resin composition is improved. As a result, when manufacturing press-molded articles of P3HA-based resin, excellent release properties are achieved, and the press molding temperature or press molding pressure can be reduced.

[0067] Furthermore, the silicon-based coating treatment is not particularly limited, but examples include silicone resin coating treatment and organopolysilazane coating treatment.

[0068] Examples of resins used in the silicone resin coating treatment include organopolysiloxanes. Examples of organopolysiloxanes include dimethylpolysiloxanes. Since organopolysiloxanes form a glass film and hard surface through a de-alcoholization reaction, they can be preferably used in silicon-based coating treatments.

[0069] Examples of polysilazanes used in the organopolysilazane coating treatment include dimethylpolysilazane. Since the polysilazane forms a glass film and hard surface through a deammonia reaction, it can be preferably used as a silicon-based coating treatment.

[0070] Furthermore, the thickness of the film formed by the silicon-based coating treatment is not particularly limited as long as the above-mentioned effects are achieved, but it is preferably 0.5 μm to 15 μm, and more preferably 1 μm to 5 μm.

[0071] Furthermore, in this manufacturing method, it is preferable that the molded surface is treated with a fluorine-based coating. The fluorine-based resin used in the fluorine-based coating treatment is not particularly limited, but examples include perfluoroalkoxyalkanes (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), and polytetrafluoroethylene (PTFE).

[0072] Furthermore, the fluorine-based coating treatment may be used in combination with a metal surface coating treatment. For example, it is preferable that the molded surface is subjected to a plating treatment that forms a metal coating in which fluorine-based resin is dispersed. That is, it is preferable that the molded surface is subjected to a composite plating treatment of fluorine-based resin and metal. The fluorine-based resin is preferably in the form of particles.

[0073] The plating treatment applied to the mold surface improves the slipperiness of the molten resin composition against the mold surface. Therefore, the fluidity of the molten resin composition is improved even when the press molding temperature or press molding pressure is reduced. As a result, when manufacturing press-molded articles of P3HA resin, excellent release properties are achieved, and the press molding temperature or press molding pressure can be reduced.

[0074] The fluororesin content in the metal coating is not particularly limited as long as the above-described effects are achieved, but it is preferably 1 vol% to 50 vol%, and more preferably 5 vol% to 30 vol%.

[0075] Furthermore, the thickness of the metal coating is not particularly limited as long as it achieves the effects described above, but it is preferably 1 μm to 50 μm, and more preferably 3 μm to 20 μm.

[0076] Furthermore, the film formed by the surface treatment may be a composite film of a metal film and a fluororesin film. The metal constituting the metal film is not particularly limited, but it is preferably one or more selected from the group consisting of nickel-based metals, chromium-based metals, iron-based metals, and alumina-based metals.

[0077] In this manufacturing method, a preferred embodiment of the plating treatment is a so-called nickel-Teflon® plating treatment (nickel-PTFE composite plating) in which PTFE particles are uniformly dispersed in a nickel plating film.

[0078] Furthermore, in this manufacturing method, it is preferable that the molded surface is subjected to both (a) roughening treatment and (b) silicon-based coating treatment or fluorine-based coating treatment so that the average length RSm falls within the specified numerical range. The molded surface may be (1) a surface that has been subjected to silicon-based coating treatment or fluorine-based coating treatment before the roughening treatment, or (2) a surface that has been subjected to silicon-based coating treatment or fluorine-based coating treatment after the roughening treatment. In case (1), the roughening treatment may cause partial peeling of the film due to the silicon-based coating treatment or fluorine-based coating treatment, while in case (2), the adhesion of the film due to the silicon-based coating treatment or fluorine-based coating treatment is improved when the roughening treatment is performed before the silicon-based coating treatment or fluorine-based coating treatment, so (2) is more preferable.

[0079] [(Press) molded product manufacturing equipment] This manufacturing apparatus is configured to implement this manufacturing method. Figure 2 is a schematic diagram showing the general configuration of this manufacturing apparatus.

[0080] The manufacturing apparatus 10 includes a pair of molds 30 for filling with a molten resin composition containing P3HA resin, as shown in Figure 1. In Figure 2, the core mold 32 is shown among the pair of molds 30 shown in Figure 1. The manufacturing apparatus 10 includes a molten resin generation unit 1, a supply unit 2, and a molding unit (not shown).

[0081] The molten resin production unit 1 generates a molten resin composition by heating a P3HA-based resin composition. The molten resin production unit 1 is equipped with a raw material input unit for inputting the raw materials of the P3HA-based resin composition. The molten resin production unit 1 is equipped with a molten kneading device for molten and kneading the raw materials input from the raw material input unit. The molten resin production unit 1 may also be equipped with a mixing device for mixing the raw materials as needed. The molten kneading device and mixing device can be exemplified by the equipment described above.

[0082] The supply unit 2 has a discharge unit 2a that discharges the molten resin composition produced in the molten resin generation unit 1. The discharge unit 2a can be exemplified by the configuration of the discharge unit described above. The supply unit 2 supplies the molten resin composition between the pair of molds by the discharge unit 2a. In the configuration shown in Figure 2, the supply unit 2 is configured to discharge the molten resin composition from the discharge unit 2a to the core mold 32. After a predetermined amount of molten resin composition is supplied to the core mold 32, the cavity mold 31 shown in Figure 1 is placed on the core mold 32, thereby supplying the molten resin composition between the pair of molds.

[0083] Although not shown in Figure 2, the manufacturing apparatus 10 also includes a molding section for performing the press molding process. This molding section closes a pair of molds 30 shown in Figure 1, press-moldes a flowable molten resin composition P, and cools it. The molding section includes a hot press molding machine that heat-presses the pair of molds, and a cooling device that cools the pair of molds after the heat pressing is complete. The hot press machine and the cooling device can be any device used in press molding. For example, the cooling device may include a pair of cooling plates that clamp the pair of molds, and the cooling plates may be used to cool and press the pair of molds.

[0084] Since this manufacturing apparatus is equipped with a pair of molds 30 as shown in Figure 1, it achieves the same effects as this manufacturing method.

[0085] [P3HA resin] This section describes the P3HA resin contained in the resin composition used in this manufacturing method and apparatus. In this specification, "P3HA resin" refers to 3-hydroxyalkanoic acid represented by the general formula: [-CHR-CH2-CO-O-] (wherein R is C n H 2n+1 It is a polyhydroxyalkanoate containing an alkyl group represented by , where n is an integer between 1 and 15 (inclusive), as a repeating unit.

[0086] More specifically, the P3HA resin preferably contains 3-hydroxybutyrate (3HB) units. The P3HA resin containing 3HB units is, for example, one or more selected from the group consisting of poly(3-hydroxybutyrate) (P3HB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P3HB3HV), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (P3HB3HV3HH), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly(3-hydroxybutyrate-co-3-hydroxydecanoate).

[0087] The P3HA-based resin may contain only one type, or it may contain two or more types.

[0088] As for P3HA resins, P3HA resins produced by microorganisms (microbially produced P3HA resins) are preferred. Microbially produced P3HA resins are usually composed only of D-isomers (R-isomers) of polyhydroxyalkanoate monomer units. Among microbially produced P3HA resins, P3HB, P3HB3HH, P3HB3HV, P3HB3HV3HH, and P3HB4HB are preferred due to their ease of industrial production, and P3HB, P3HB3HH, P3HB3HV, and P3HB4HB are more preferred.

[0089] The microorganisms that produce microbially produced P3HA resins are not particularly limited as long as they are microorganisms capable of producing P3HA resins. For example, the first P3HB-producing bacterium was Bacillus megaterium, discovered in 1925, and other examples include natural microorganisms such as Cupriavidus necator (formerly classified as Alcaligenes eutrophus, Ralstonia eutropha) and Alcaligenes latus. It is known that P3HB accumulates within the cells of these microorganisms.

[0090] Furthermore, known microorganisms that produce copolymers of hydroxybutyrate and other hydroxyalkanoates include Aeromonas caviae, which produces P3HB3HV and P3HB3HH, and Alcaligenes eutrophus, which produces P3HB4HB. In particular, with respect to P3HB3HH, Alcaligenes eutrophus AC32 strain (FERM BP-6038) (T.Fukui, Y.Doi, J.Bateriol., 179, p4821-4830 (1997)), into which genes of the P3HA resin synthase group have been introduced, are more preferred in order to increase the productivity of P3HB3HH. Microbial cells that have accumulated P3HB3HH in their cells by culturing these microorganisms under appropriate conditions are used. In addition to the above, genetically modified microorganisms into which various P3HA resin synthesis-related genes can be introduced may be used, depending on the P3HA resin to be produced, or the culture conditions, including the type of substrate, may be optimized.

[0091] Furthermore, the P3HA resin contains at least one copolymer of 3HB units and other hydroxyalkanoate units, and the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin are preferably 90.0 to 99.0 mol%, more preferably 91.0 to 98.5 mol%, more preferably 92.0 to 98.5 mol%, and even more preferably 93.0 to 98.0 mol%, of the total repeating units (100 mol%).

[0092] When the composition ratio of 3HB repeating units is 90.0 mol% or higher, the rigidity of the P3HA resin is further improved, the crystallization rate is increased, burrs are reduced, and productivity tends to improve. On the other hand, when the composition ratio of 3HB repeating units is 99.0 mol% or lower, the melting point is below the thermal decomposition temperature, enabling stable and continuous production. The monomer composition ratio of P3HA resin can be measured by gas chromatography, etc. (see, for example, International Publication No. 2014 / 020838).

[0093] The molecular weight of the P3HA resin is not particularly limited, as long as it exhibits substantially sufficient physical properties for the intended application. The weight-average molecular weight range of the P3HA resin is preferably 100,000 to 1,000,000, more preferably 150,000 to 700,000, even more preferably 200,000 to 500,000, and particularly preferably 250,000 to 450,000. A weight-average molecular weight of 100,000 or more provides adequate mechanical strength. Furthermore, a molecular weight of 1,000,000 or less suppresses the increase in melt viscosity and provides excellent moldability.

[0094] The weight-average molecular weight can be determined using gel permeation chromatography (GPC) (Shodex GPC-101, Showa Denko Corporation), with a polystyrene gel column (Shodex K-804, Showa Denko Corporation) and chloroform as the mobile phase, expressed as the molecular weight in polystyrene equivalent. Calibration curves are created using polystyrene with weight-average molecular weights of 31,400, 197,000, 668,000, and 1,920,000. Any column suitable for measuring the aforementioned molecular weights can be used in the GPC.

[0095] The resin composition may also contain a second P3HA resin in addition to the P3HA resin. The second P3HA resin contains at least one copolymer of 3HB units and other hydroxyalkanoate units, and the amount of 3HB units in the poly(3-hydroxyalkanoate) resin is preferably 65.0 to 90.0 mol%, more preferably 68.0 to 88.0 mol%, and even more preferably 70.0 to 85.0 mol% of the total repeating units (100 mol%). The resin composition further contains a second P3HA resin, resulting in superior toughness of the molded article.

[0096] The second P3HA-based resin is not particularly limited, as long as it is different from the aforementioned P3HA-based resin. Examples of the second P3HA-based resin include the resins exemplified above as P3HA-based resins.

[0097] The content of the second P3HA resin is not particularly limited, but is preferably 50 parts by weight or less, more preferably 45 parts by weight or less, and even more preferably 40 parts by weight or less, per 100 parts by weight of the total P3HA resin. The lower limit of the content of the second P3HA resin is not particularly limited and may be 0 parts by weight. The P3HA resin described above can be used as the second P3HA resin. In this specification, "total P3HA resin" refers to all P3HA resin contained in the resin composition in this manufacturing method.

[0098] The resin composition may contain other resins besides P3HA resins, as long as they do not impair the effects of the present invention. Examples of such other resins include aliphatic polyester resins such as polybutylene succinate adipate, polybutylene succinate, polycaprolactone, and polylactic acid, and aliphatic aromatic polyester resins such as polybutylene adipate terephthalate, polybutylene sebatate terephthalate, and polybutylene azelate terephthalate. The other resin may consist of only one type or two or more types.

[0099] The content of the other resins is not particularly limited, but is preferably 50 parts by weight or less, more preferably 40 parts by weight or less, per 100 parts by weight of the total P3HA resin. Even more preferably 30 parts by weight or less. The lower limit of the content of the other resins is not particularly limited and may be 0 parts by weight.

[0100] The resin composition does not necessarily have to contain an inorganic filler, but it is preferable that it further contains an inorganic filler. The inclusion of an inorganic filler in the resin composition improves the crystallization rate, resulting in effects such as reduced burrs and improved production cycles.

[0101] The inorganic filler is not particularly limited, but examples include talc, diatomaceous earth, white clay, clay, calcium carbonate, manganese carbonate, magnesium carbonate, barium sulfate, mica, silica, alumina, zircon, iron oxide, zinc oxide, titanium oxide, silicon nitride, boron nitride, aluminum nitride, silicon carbide, graphite, carbon black, ferrite, graphite, quartz, glass fiber, and glass particles. These may be used individually or in combination of two or more types.

[0102] The inorganic filler content is, for example, 0 to 60 parts by weight, preferably 5 to 50 parts by weight, more preferably 10 to 40 parts by weight, and particularly preferably 15 to 35 parts by weight, per 100 parts by weight of the total P3HA resin. When the inorganic filler content is within the above range, it is possible to achieve both a sufficient crystallization rate and toughness.

[0103] Furthermore, the resin composition may contain additives that can be used together with the P3HA resin, provided that they do not inhibit the effects described above. Examples of such additives include colorants such as pigments and dyes, odor absorbers such as activated carbon and zeolites, fragrances such as vanillin and dextrin, plasticizers, antioxidants, weather-resistant modifiers, UV absorbers, crystal nucleating agents, lubricants, mold release agents, water repellents, antibacterial agents, and sliding properties modifiers. The composition may contain only one additive, or two or more additives. The content of these additives can be appropriately determined by those skilled in the art depending on their intended use.

[0104] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0105] In other words, one embodiment of the present invention is as follows: <1> A method for manufacturing a molded article, comprising a molding step of molding a resin composition containing a thermoplastic resin using a mold, wherein the molding surface of the mold has an average length RSm in the range of 100 μm to 400 μm. <2> The molded surface of the aforementioned mold has an arithmetic mean roughness Ra in the range of 0.1 μm to 3.0 μm, and a maximum height Rz in the range of 0.5 μm to 20.0 μm. <1> A method for manufacturing a molded article. <3> The molded body has a deep bottom structure. <1> or <2> A method for manufacturing a molded article. <4> The surface free energy of the molding surface of the mold is 26.0 mN / m or less. <1> ~ <3> A method for manufacturing any of the following molded articles. <5> The molding surface of the mold is treated with a silicon-based coating or a fluorine-based coating. <1> ~ <4> A method for manufacturing any of the following molded articles. <6> The aforementioned thermoplastic resin is a poly(3-hydroxyalkanoate) resin. <1> ~ <5> A method for manufacturing any of the following molded articles. <7> A manufacturing apparatus comprising a mold for molding a resin composition containing a thermoplastic resin, wherein the molding surface of the mold has an average length RSm in the range of 100 μm to 400 μm. [Examples]

[0106] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0107] (Comparative Example 1) A pair of molds 30 (cavity mold 31 and core mold 32) shown in Figure 1 were used as the mold material. Aluminum alloy (A7075) was used for both the cavity mold 31 and the core mold 32. After blasting, the entire molding surface 31A and 32A was coated with a 5 μm thick nickel-PTFE composite plating (PTFE content 30 vol%), which is a fluorine-based coating treatment.

[0108] Furthermore, the mold 30 used was designed so that the clearance between the molding surface 31A of the cavity mold 31 and the molding surface 32A of the core mold 32 was 0.30 mm, that is, so that the design film thickness of the press-formed body A was 0.30 mm. The press-formed body A was designed so that the diameter B of the bottom A1 was 57.5 mm, the height C was 120 mm, and the slope of the side wall A2 was 6°. The ratio C / B is 2.09.

[0109] For molded surfaces 31A and 32A, the arithmetic mean roughness Ra, maximum height Rz, and average length RSm were measured in multiple sections according to JIS B 0601-2001, and their average values ​​were calculated. As a result, the arithmetic mean roughness Ra was 0.44 μm, the maximum height Rz was 3.01 μm, and the average length RSm was 63.5 μm.

[0110] Furthermore, for molded surfaces 31A and 32A, pure water and diiodomethane (CH2I2) were dropped onto the mold surface using a contact angle meter (PCA-11, manufactured by Kyowa Interface Science Co., Ltd.), and the contact angle θ between each droplet and the mold surface was measured. From the contact angle θ, the surface free energy of the sample was calculated using the Owens-Wendt method.

[0111] Specifically, by substituting the contact angle θ of each droplet and the surface free energy γL of the liquid into equations (1) and (2) below and solving the simultaneous equations, the surface free energy γ of the solid (sample) can be found. S The following was determined. In equations (1) and (2), γ is the surface free energy, L is the symbol for liquid and S is the symbol for solid, and d and h are the symbols for the dispersion component and hydrogen bonding component of the surface free energy, respectively.

[0112] The calculated surface free energy was 24.8 mN / m.

[0113]

number

[0114] (Comparative Example 2) In the pair of molds 30 shown in Figure 1, the entire area of ​​the molding surfaces 31A and 32A was subjected to blast treatment, and the average values ​​of the arithmetic mean roughness Ra, maximum height Rz, and average length RSm measured over multiple sections were 0.76 μm, 5.15 μm, and 80.4 μm, respectively. In all other respects, the molds 30 were the same as those used in Comparative Example 1.

[0115] The surface free energy was calculated to be 22.9 mN / m using the same method as in Comparative Example 1.

[0116] (Comparative Example 3) In the pair of molds 30 shown in Figure 1, the entire molding surfaces 31A and 32A were subjected to blast treatment, followed by a glass film coating of dimethylpolysiloxane, a silicon-based coating treatment, with a film thickness of 1 μm. For the molding surfaces 31A and 32A, the arithmetic mean roughness Ra, maximum height Rz, and average length RSm were measured over multiple sections, and their average values ​​were calculated. As a result, the arithmetic mean roughness Ra was 0.49 μm, the maximum height Rz was 3.37 μm, and the average length RSm was 59.9 μm. All other aspects were the same as in Comparative Example 1, using the same pair of molds 30.

[0117] The surface free energy was calculated to be 15.9 mN / m, using the same method as in Comparative Example 1.

[0118] (Comparative Example 4) A pair of molds 30 identical to those used in Comparative Example 3 was used, except that the entire surface of the molding surfaces 31A and 32A was blast-treated, and the average values ​​of the arithmetic mean roughness Ra, maximum height Rz, and average length RSm measured over multiple sections were 0.72 μm, 4.81 μm, and 81.6 μm, respectively.

[0119] The surface free energy was calculated to be 15.2 mN / m, using the same method as in Comparative Example 1.

[0120] (Example 1) In the pair of molds 30 shown in Figure 1, the entire area of ​​the molding surfaces 31A and 32A was subjected to blast treatment, and the average values ​​of the arithmetic mean roughness Ra, maximum height Rz, and average length RSm measured over multiple sections were 0.77 μm, 4.90 μm, and 192.6 μm, respectively. In all other respects, the same pair of molds 30 as in Comparative Example 1 were used.

[0121] The surface free energy was calculated to be 24.4 mN / m, using the same method as in Comparative Example 1.

[0122] (Example 2) In the pair of molds 30 shown in Figure 1, the entire area of ​​the molding surfaces 31A and 32A was subjected to blast treatment, and the average values ​​of the arithmetic mean roughness Ra, maximum height Rz, and average length RSm measured over multiple sections were 1.33 μm, 7.54 μm, and 205.3 μm, respectively. In all other respects, the same pair of molds 30 as in Comparative Example 1 were used.

[0123] The surface free energy was calculated to be 22.7 mN / m, using the same method as in Comparative Example 1.

[0124] (Example 3) In the pair of molds 30 shown in Figure 1, the entire area of ​​the molding surfaces 31A and 32A was subjected to blast treatment, and the average values ​​of the arithmetic mean roughness Ra, maximum height Rz, and average length RSm measured over multiple sections were 1.91 μm, 10.57 μm, and 198.2 μm, respectively. In all other respects, the same pair of molds 30 as in Comparative Example 1 were used.

[0125] The surface free energy was calculated to be 21.5 mN / m using the same method as in Comparative Example 1.

[0126] (Example 4) In the pair of molds 30 shown in Figure 1, the entire area of ​​the molding surfaces 31A and 32A was subjected to blast treatment, and the average values ​​of the arithmetic mean roughness Ra, maximum height Rz, and average length RSm measured over multiple sections were 2.13 μm, 11.39 μm, and 293.6 μm, respectively. In all other respects, the same pair of molds 30 as in Comparative Example 1 were used.

[0127] The surface free energy was calculated to be 20.3 mN / m, using the same method as in Comparative Example 1.

[0128] (Example 5) In the pair of molds 30 shown in Figure 1, the entire area of ​​the molding surfaces 31A and 32A was subjected to blast treatment, and the average values ​​of the arithmetic mean roughness Ra, maximum height Rz, and average length RSm measured over multiple sections were 0.76 μm, 4.67 μm, and 202.1 μm, respectively. In all other respects, the same pair of molds 30 as in Comparative Example 3 were used.

[0129] The surface free energy was calculated to be 15.6 mN / m, using the same method as in Comparative Example 1.

[0130] (Example 6) In the pair of molds 30 shown in Figure 1, the entire area of ​​the molding surfaces 31A and 32A was subjected to blast treatment, and the average values ​​of the arithmetic mean roughness Ra, maximum height Rz, and average length RSm measured over multiple sections were 1.35 μm, 7.80 μm, and 199.1 μm, respectively. In all other respects, the same pair of molds 30 as in Comparative Example 3 were used.

[0131] The surface free energy was calculated to be 14.6 mN / m, using the same method as in Comparative Example 1.

[0132] (Example 7) In the pair of molds 30 shown in Figure 1, the entire area of ​​the molding surfaces 31A and 32A was subjected to blast treatment, and the average values ​​of the arithmetic mean roughness Ra, maximum height Rz, and average length RSm measured over multiple sections were 2.00 μm, 10.80 μm, and 203.0 μm, respectively. In all other respects, the same pair of molds 30 as in Comparative Example 3 were used.

[0133] The surface free energy was calculated to be 14.2 mN / m, using the same method as in Comparative Example 1.

[0134] (Example 8) In the pair of molds 30 shown in Figure 1, the entire area of ​​the molding surfaces 31A and 32A was subjected to blast treatment, and the average values ​​of the arithmetic mean roughness Ra, maximum height Rz, and average length RSm measured over multiple sections were 2.03 μm, 10.97 μm, and 291.8 μm, respectively. In all other respects, the same pair of molds 30 as in Comparative Example 3 were used.

[0135] The surface free energy was calculated to be 13.8 mN / m, using the same method as in Comparative Example 1.

[0136] (Evaluation method) In the following explanation, we will refer to the mold 30 shown in Figure 1 as appropriate.

[0137] <Method for manufacturing press-formed products> Using a tabletop plunger-type melting and dispensing machine (manufactured by Nakatsuji Mold Industry Co., Ltd.), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (sometimes referred to as P3HB3HH) (weight-average molecular weight Mw 400,000, 3HH ratio 6 mol%) was heated to 160°C to form a molten resin. The molten P3HB3HH resin was then dispensed into a core mold 32 that had been preheated to 150°C, thereby supplying the core mold 32 with the molten P3HB3HH resin. Next, the core mold 32, which had been supplied with the molten P3HB3HH resin, was closed with a cavity mold 31, which had also been heated to 150°C, thereby supplying the molten resin between the pair of molds 30. The pair of molds 30, which had been supplied with the molten P3HB3HH resin, were then subjected to hot pressing using a hot press molding device (Mikado Technos Co., Ltd., VS38-2525) at a press pressure of 125 kN for a pressing time of 20 seconds. The pair of molds 30, which had just been heat-pressed, were immediately sandwiched between upper and lower cooling plates heated to 25°C, and press molding was performed by cooling press at a press pressure of 30kN for 300 seconds. Immediately after press molding, the molds were opened, and the press-molded body remaining in the core mold 32 was released and removed.

[0138] <Evaluation of mold release properties> The above-described method for producing press-molded bodies was carried out using the pairs of molds 30 from Comparative Examples 1-4 and Examples 1-8. When removing the press-molded bodies, a vacuum pad with an outer diameter of 50 mm (manufactured by Nippon Pisco, VP50R) was used to adsorb the press-molded bodies at a vacuum of approximately -100 kPa, and then the press-molded bodies remaining in the core mold 32 were released by pulling the vacuum pad upwards.

[0139] The release properties of press-molded products were evaluated by repeating the process of fabricating press-molded products and releasing them using a vacuum pad 10 times, and determining the number of times the release was successful without problems out of 10 attempts.

[0140] The evaluation results are shown in Table 1.

[0141] [Table 1]

[0142] As shown in Table 1, in the methods using the pair of molds 30 in Comparative Examples 1 to 4, the average length RSm was outside the range of 100 μm to 400 μm, resulting in the press-molded body being strongly adhered to the core mold 32 and poor release properties. Consequently, when the press-molded body was sucked up by the vacuum pad and pulled upward, the vacuum pad detached from the press-molded body, and the press-molded body could not be released even once out of 10 attempts. In other words, it was difficult to stably manufacture press-molded bodies using the methods using the pair of molds 30 in Comparative Examples 1 to 4.

[0143] In contrast, the methods using the pair of molds 30 in Examples 1 to 8, in which the average length RSm is in the range of 100 μm to 400 μm, showed better release properties than the pair of molds 30 in Comparative Examples 1 to 4. Specifically, when demolding with a vacuum pad was repeated 10 times, the number of successful demolding attempts increased, with successful demolding occurring 6 times in Example 1, 10 times in Example 2, 10 times in Example 3, 7 times in Example 4, 7 times in Example 5, 10 times in Example 6, 10 times in Example 7, and 6 times in Example 8. In other words, it was found that the methods using the pair of molds 30 in Examples 1 to 8 showed improved demolding properties, making it possible to manufacture press-molded products more stably. Among Examples 1 to 8, when the arithmetic mean roughness Ra exceeded 1 μm and the average length RSm was 200 μm ± 6 μm (Examples 2, 3, 6, and 7), the number of successful demolding attempts was 10, indicating even better demolding properties. [Industrial applicability]

[0144] The present invention can be suitably used in the field of manufacturing molded articles using thermoplastic resins, and particularly in the field of manufacturing press-molded articles using P3HA-based resins. [Explanation of Symbols]

[0145] 1. Molten resin generation section 2 Supply section 2a Discharge part 10 Manufacturing equipment 30 molds 31 Cavity type 31A Molding surface 32-core type 32A Molding surface A Press-formed body A1 bottom A2 side wall

Claims

1. The process includes a molding step in which a resin composition containing a thermoplastic resin is molded using a mold. A method for manufacturing a molded article, wherein the molding surface of the mold has an average length RSm in the range of 100 μm to 400 μm.

2. The method for manufacturing a molded article according to claim 1, wherein the molded surface of the mold has an arithmetic mean roughness Ra in the range of 0.1 μm to 3.0 μm and a maximum height Rz in the range of 0.5 μm to 20.0 μm.

3. The method for manufacturing a molded article according to claim 1 or 2, wherein the molded article has a deep bottom structure.

4. The method for manufacturing a molded article according to claim 1 or 2, wherein the surface free energy of the molded surface of the mold is 26.0 mN / m or less.

5. The method for manufacturing a molded article according to claim 1 or 2, wherein the molding surface of the mold is subjected to a silicon-based coating treatment or a fluorine-based coating treatment.

6. The method for producing a molded article according to claim 1 or 2, wherein the thermoplastic resin is a poly(3-hydroxyalkanoate) resin.

7. A mold for molding a resin composition containing a thermoplastic resin, A manufacturing apparatus in which the molding surface of the mold has an average length RSm in the range of 100 μm to 400 μm.

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